Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
  • C21D1/26—Methods of annealing
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  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
  • C21D1/84—Controlled slow cooling
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D6/00—Heat treatment of ferrous alloys
  • C21D6/002—Heat treatment of ferrous alloys containing Cr
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D6/00—Heat treatment of ferrous alloys
  • C21D6/005—Heat treatment of ferrous alloys containing Mn
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D6/00—Heat treatment of ferrous alloys
  • C21D6/008—Heat treatment of ferrous alloys containing Si
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/12—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
  • C21D8/1205—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties involving particular fabrication steps or treatments of ingots or slabs
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/12—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
  • C21D8/1216—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties characterised by the working steps
  • C21D8/1222—Hot rolling
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/12—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
  • C21D8/1216—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties characterised by the working steps
  • C21D8/1233—Cold rolling
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/12—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
  • C21D8/1244—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties characterised by the heat treatment
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/12—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
  • C21D8/1244—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties characterised by the heat treatment
  • C21D8/1261—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties characterised by the heat treatment following hot rolling
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/12—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
  • C21D8/1244—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties characterised by the heat treatment
  • C21D8/1272—Final recrystallisation annealing
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/12—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
  • C21D8/1277—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties involving a particular surface treatment
  • C21D8/1283—Application of a separating or insulating coating
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/004—Very low carbon steels, i.e. having a carbon content of less than 0,01%
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/20—Ferrous alloys, e.g. steel alloys containing chromium with copper
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/34—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of silicon
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
  • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
  • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
  • H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
  • H01F1/14—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys
  • H01F1/147—Alloys characterised by their composition
  • H01F1/14766—Fe-Si based alloys
  • H01F1/14775—Fe-Si based alloys in the form of sheets
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
  • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
  • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
  • H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
  • H01F1/14—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys
  • H01F1/147—Alloys characterised by their composition
  • H01F1/14766—Fe-Si based alloys
  • H01F1/14791—Fe-Si-Al based alloys, e.g. Sendust
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D2211/00—Microstructure comprising significant phases
  • C21D2211/005—Ferrite
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C2202/00—Physical properties
  • C22C2202/02—Magnetic

Definitions

• the present invention relates to a non-oriented electrical steel sheet and a manufacturing method thereof. Specifically, the present invention relates to a non-oriented electrical steel sheet and a manufacturing method thereof that have low iron losses specifically a low eddy current loss while having good mechanical properties. Therefore, intense research and development endeavors are put in higher performance properties have been required for a non-oriented electrical steel sheet to be used as an iron core material of a electrical machine due to a worldwide increase in achievement of energy saving of an electrical apparatus.
• This invention relates to the second option, namely the reduction of eddy current losses for an electrical machine.
• the first track consists of reducing the thicknesses of the steel sheets used in the electrical machines such as to have the thickness of the steel sheet below 0.35mm or even lower.
• the second track consists of optimizing the elemental composition of the steel sheet such as by increase the amount of alloying elements to restrict the eddy current losses.
• alloying elements such as, the Aluminum and Manganese ones have attractive mechanical and magnetic properties while making it possible to significantly reduce the eddy current losses.
• addition of alloying elements can be done up to a limit because after a certain percentage presence alloying elements will impacts the hysteresis losses and the magnetic polarization.
• US2021/371948 is non - oriented electrical steel sheet with an average magnetostriction ⁇ p - p at 400 Hz and 1.0 T of not more than 4.5x10 -6 , and area ratio of recrystallized grains at a section in rolling direction of steel sheet of 40 to 95 % and an average grain size of 10 to 40 microns is obtained by subjecting a steel slab containing , in mass % , C : not more than 0.005 % , Si : 2.8 to 6.5 % , Mn : 0.05 to 2.0% , Al : not more than 3.0 % , P : not more than 0.20 % , S : not more than 0.005 % , N : not more than 0.005 % , Ti : not more than 0.003
• US2021/371948 does not demonstrate the total elongation and eddy current loss at all.
• the purpose of the present invention is to solve these problems by making non-oriented electrical steel sheets that have a percentage of eddy current loss in total iron loss of less than 25%, and preferably less than 23% and more preferably from 18% to 22% when calculated in accordance with Bertotti method -
• the additional following properties can be also reached, alone or in combination :an ultimate tensile strength of 540MPa or more in both transversal direction as well as rolling direction and preferably more than 560MPa in both transversal direction as well as rolling direction - a yield strength from 410MPa or more in both transversal direction as well as rolling direction and preferably from 430MPa or more in both transversal direction as well as rolling direction - a total elongation of 9% or more in both transversal direction as well as rolling direction and preferably more than or equal to 11% in both transversal direction as well as rolling direction - a magnetic polarization
• such steel can also have a good suitability for rolling with good punchability and coatability.
• Another object of the present invention is also to make available a method for the manufacturing of these sheets that is compatible with conventional industrial applications while being robust towards manufacturing parameters shifts.
• the chemical composition of the non-oriented electrical steel comprises of the following elements, in weight percent: Carbon is present in the steel of present invention is from 0.0001% to 0.007%. Carbon is a precipitate forming element that is why detrimental for the magnetic properties of the present steel. Hence the presence of Carbon in the present steel is from 0.0001% to 0.007%. Since the Carbon promotes magnetic aging the preferred content of Carbon according to the present invention is from 0.002% to 0.007% and more preferably from 0.002% to 0.005%.
• Manganese content of the steel of present invention is from 0.17% to 0.4%. Manganese provides solid solution strengthening and reducing the iron loss by increasing specific resistance.
• the preferred limit for the presence of Manganese is from 0.18% to 0.3% and more preferably 0.19% to 0.23%.
• Silicon content of the steel of present invention is from 3% to 3.6%. Silicon is an element that contributes to increasing the strength by solid solution strengthening and is a key element to reduce eddy current loss of iron loss by increasing specific resistance of steel. The mentioned effects requires a minimum Silicon content of at least 3%. However, when silicon content is in an amount exceeding 3.6% causes the rolling to be difficult and the magnetic induction of the steel will be significantly lowered.
• the preferred limit for the presence of Silicon is from 3.1% to 3.5% and more preferably from 3.1% to 3.4%.
• the content of the Aluminum is from 0.7% to 1.3%. Aluminum increases the electrical resistivity of the material and can effectively reduce the iron loss of steel. When the content of Aluminum is present more than 1.3%, the magnetic induction of the steel will be significantly reduced, and it is also detrimental to the rollability of cold rolling of the steel of present invention.
• the preferred limit for the presence of Aluminium is from 0.85% and 1.1% and more preferably from 0.9% to 1.05%. Sulfur is not an essential element but may be contained as an impurity in steel and from point of view of the present invention the Sulfur content is preferably as low as possible but 0.006% or less from the viewpoint of manufacturing cost.
• Phosphorus constituent of the Steel of present invention is from 0% to 0.15%, Phosphorus reduces the hot and cold ductility, particularly due to its tendency to segregate at the grain boundaries or co-segregate with Manganese. For these reasons, its content is limited to 0.15% and preferably lower than 0.09%. Nitrogen is limited to 0.09% to minimize the precipitation of Aluminum nitrides during solidification which are detrimental for magnetic properties of the steel. Titanium is an optional element and when added to the Steel of present invention is from 0% to 0.1%. It forms Titanium-nitrides appearing during solidification of the cast product.
• Titanium is so limited to 0.1% to avoid the formation of Titanium-nitrides detrimental for magnetic properties of the steel of present invention. In case the Titanium content below 0.001% does not impart any effect on the steel of present invention.
• Niobium is present in the Steel of present invention from 0% to 0.1% and suitable for forming carbo-nitrides to increase strength of the Steel of present invention by precipitation hardening. Niobium will also impact the size of microstructural components through its precipitation as carbo- nitrides. However, Niobium content above 0.1% is not economically interesting as a saturation effect.
• Vanadium is present in the Steel of present invention from 0% to 0.1% and is effective in enhancing the strength of steel by forming carbides or carbo-nitrides and the upper limit is 0.1% from economic points of view.
• Chromium is an optional element for the steel of present invention is from 0% to 1%. Chromium provide strength to the steel by solid solution strengthening but when used above 1% impairs the magnetic properties of the steel. In a preferred embodiment, chromium content is at least 0.01%.
• Molybdenum is an optional element that constitutes 0% to 0.5% of the Steel of present invention. Mo has an effect of coarsening carbide and thus reducing the iron loss. When it exceeds 0.5%, the effect of improving the iron loss is saturated.
• Tungsten is an optional element that constitutes 0% to 0.1% of the Steel of present invention. Tungsten has an effect of coarsening carbide and reducing the iron loss, like Mo. However, when the addition amount is less than 0.001 mass%, the above effect cannot be obtained sufficiently, while when it exceeds 0.1 wt.%, the effect of improving the iron loss is saturated.
• Cobalt is an optional element that constitutes 0% to 1% of the Steel of present invention. Cobalt is an element increasing the magnetic moment of Fe alloy and has an effect of increasing a magnetic flux density and reducing the iron loss. However, when the addition amount is less than 0.01 wt.%, the above effects cannot be obtained sufficiently, while when it exceeds 1 wt.%, the raw material cost is largely increased.
• Arsenic is an optional element that constitutes 0% to 0.05% of the Steel of present invention.
• a grain boundary segregation element and has an effect of improving the texture and thus reducing the iron loss.
• the above effect is obtained by the addition of not less than 0.001 wt.%.
• Nickel may be added as an optional element in an amount of 0% to 1% to increase the strength of the steel present invention and to improve its strength and elongation. However, when its content is above 1%, Nickel causes ductility deterioration.
• nickel content remains below 0.04%.
• Copper may be added as an optional element in an amount of 0% to 1% to increase the strength and elongation of the of Steel of present invention. However, when its content is above 1%, it can degrade the surface aspects. In a preferred embodiment, copper content is at least 0.01%.
• Boron is an optional element for the steel of present invention and may be present from 0% to 0.05%. Boron forms boro-nitirides and impart additional strength to steel of present invention when added in an amount of at least 0.0001%. Calcium may be present in the steel of present invention optionally and may be from 0.001% to 0.01%%.
• Sn , Pb or Sb contributes towards the refining of the Steel by binding the detrimental Sulfur content in globular form thereby retarding the harmful effect of Sulfur.
• Other elements such as Sn , Pb or Sb can be added individually or in combination in the following proportions: Sn ⁇ 0.2%, Pb ⁇ 0.2% and Sb ⁇ 0.2%. Up to the maximum content levels indicated, these elements make it possible to refine the grain during solidification. In a preferred embodiment, Sn content is below 0.04%. The remainder of the composition of the steel consists of iron and inevitable impurities resulting from processing.
• the non-oriented electrical steel sheet according to the invention mandatorily contains Silicon, Manganese and Aluminum such that the total content is from 3.85% to 5.5wt.%.
• Si, Mn and Al When the total content of Si, Mn and Al is less than 3.85%, it is not possible to achieve the mechanical properties with the magnetic properties. However, when the total content of Si , Mn and Al exceeds 5.5%, steel is hardened and the rolling becomes difficult.
• the preferred limit for the presence of Si, Mn and Al is from 3.9% to 5.2% and more preferably from 4% to 5%.
• the steel of present invention has a recrystallized microstructural region from 80% to 100% in area fraction with grains having an average grain size from 20 microns to 110 microns.
• the recrystallized structure with a high degree of recrystallization is due to the homogenous Silicon enrichment which improves magnetic properties of the steel of present invention.
• a controlled grain size ensures the mechanical properties in both transverse and rolling direction.
• the preferred degree of recrystallization is from 90% to 100%.
• the preferred an average grain size for the present invention is from 20 microns to 100 microns and more preferably from 20 microns to 90 microns.
• the steel of present invention may have a non-recrystallized microstructural region from 0% to 20% in area fraction and the preferred degree of non-recrystallization is from 0% to 10% and more preferably from 0% to 5%
• the microstructure of the non-oriented electrical steel is free from microstructural components such as martensite, bainite, pearlite and cementite.
• the steel according to the invention can be manufactured by any suitable methods. It is however preferable to use the method according to the invention that will be detailed, as a non-limitative example. Such preferred method consists in providing a semi-finished casting of steel with a chemical composition of the steel according to the invention.
• the casting can be done either into ingots or continuously in form of thin slabs or thin strips, i.e. with a thickness ranging from approximately 240mm or less for any form of casting.
• the cast in form of a slab is casted with the chemical composition according to the invention and then it is reheated, the Slab Reheating Temperature lying from 1100°C to 1250°C until the temperature is homogeneous through the whole slab. Below 1100°C, rolling becomes difficult and forces on the mill will be too high. Above 1250°C, high silicon grades become very soft and might show some sagging and thus become difficult to handle.
• the preferred slab reheating temperature is from 1100°C to 1200°C and more preferably from 1120°C to 1180°C.
• the hot rolling finishing temperature plays a role on the final hot rolled microstructure and takes place from 780°C to 860°C.
• the Finishing Rolling Temperature is below 780°C, recrystallization is limited and the microstructure is highly deformed. Above 860°C would mean more impurities in solid solution and possible consequent precipitation and deterioration of magnetic properties as well.
• the preferred hot rolling finishing temperature is from 800°C to 860°C and more preferably 810°C to 860°C.
• the hot rolled steel sheet obtained in this manner is then cooled immediately at a cooling rate of at least 10°C/s to the Coiling Temperature of the hot rolled steel sheet which also plays a role on the hot rolled steel sheet; it takes place from 480°C to 550°C. Coiling at temperatures below 480°C will not have the proper distribution and size of the precipitates for the steel of present invention. Above 550°C, a thick oxide layer would appear, and it will cause difficulties for subsequent processing steps such as cold rolling and/or pickling.
• the cooling rate will be less than or equal to 200° C/s and more preferably the cooling rate is from 12°C/s to 75°C/s.
• the preferred Coiling Temperature is from 490°C to 540°C and more preferably 500°C to 540°C.
• the coiled hot rolled steel sheet is then cooled down to room temperature before subjecting it to optional hot band annealing.
• the hot rolled steel sheet may be subjected to an optional scale removal step to remove the scale formed during the hot rolling before optional hot band annealing.
• the hot rolled sheet then be subjected to an optional hot band annealing such hot band annealing is performed at temperatures from 650°C to 1100°C, preferably for at least 10 seconds and not more than 96 hours, the temperature preferably remaining from 750°C to 1080°C and more preferably from 790°C to 1000°C.
• the hot rolled steel sheet obtained may optionally have thickness from 0.8mm to 3.5mm and preferably from 0.9mm to 3mm and more preferably 1mm to 2.8mm.
• This hot rolled steel sheet is then subjected to cold rolling to obtain a cold rolled steel sheet with a thickness reduction from 50 to 95%.
• the thickness reduction from 60% to 95% and more preferably from 75% to 95%.
• the cold rolled steel sheet is being heat treated which will impart the steel of present invention with requisite mechanical properties and microstructure.
• the cold rolled steel sheet is then heated wherein the heating starts from room temperature, the cold rolled steel sheet being heated, at a heating rate HR1 of at least 1°C/s, to an annealing temperature Tsoak which is from 890°C to 990°C.
• the heating rate HR1 for heating is at least 2°C/s and more preferably at least 5°C/s.
• the preferred Tsoak Temperature is from 900°C to 980°C and more preferably 920°C to 970°C.
• the cold rolled steel sheet is held at Tsoak during 10 seconds to 5000 seconds to ensure a recrystallization from 80% to 100%.
• the cold rolled steel sheet is then cooled wherein cooling starts from Tsoak, the cold rolled steel sheet being cooled down, at a cooling rate CR1 from 1°C/s to 150°C/s, to a temperature T1 which is in a range from 20°C to 300°C.
• the cooling rate CR1 is from 3°C/s to 120°C/s.
• the preferred T1 temperature is from 20°C to 200°C.
• the cold rolled steel sheet thus obtained must have a thickness from 0.15 mm to 0.23 mm and more preferably from 0.16 mm to 0.22 mm and even more preferably from 0.17mm to and 0.21 mm.
• the cold rolled steel sheet is cooled down to room temperature to obtain a non-oriented electrical steel sheet.
• the non-oriented electrical steel sheet of the present invention may optionally be coated with insulation, organic coating or inorganic coating or combination of to improve isolation.
• EXAMPLES The following tests, examples, figurative exemplification and tables which are presented herein are non-restricting in nature and must be considered for purposes of illustration only and will display the advantageous features of the present invention. Steel sheets made of steels with different compositions are gathered in Table 1, where the steel sheets are produced according to process parameters as stipulated in Table 2, respectively. Thereafter, table 3 gathers the result of evaluations of obtained properties. All steels of Table 1 had a nitrogen content below 0.09%.
• Table 2 gathers the hot rolling and annealing process parameters implemented on cold rolled steel sheets to impart the steels of table 1 with requisite mechanical and magnetic properties to become a non-oriented electrical steel.
• the Inventive steels that is from I1 to I6 all are cooled after hot rolling at cooling rate 15°C/s. Further for the inventive examples the heating rate HR1 to the annealing soaking temperature is 5°C/s. The T1 temperature for all the inventive examples is 25°C while the cooling rate CR1 is at 5°C/s. All steels produced according to table 2 parameters showed a microstructure with more than 95% of recrystallization and with a grain size from 20 to 110 ⁇ m.
• the ultimate tensile strength, total elongation and yield strength are measured in accordance with NF EN ISO 6892-1 standards and the J50 magnetic properties and the total iron losses at 1T and 400Hz were measured in accordance with IEC 60404-2 standards.
• the Eddy current losses are calculated in accordance with the Bertotti Method published in the paper entitled as “General Properties of Power Losses in Soft Ferromagnetic Materials” by Giorgio Berttoti published in IEEE TRANSACTIONS ON MAGNETICS, Vol. 24, No.1 of January 1988.
• the Equation 2 identifies classical losses which is designated by (P class ) which for the purpose of this invention is referred to as Eddy current losses.
• the average grain size of the recrystallized microstructure is measured in accordance with ASTM E11296(02) standards with linear intercept method.
• MPa Eddy Trials Yield Strength
• T current (T) (W/kg) losses

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